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Task/Kaprekar-numbers/FreeBASIC/kaprekar-numbers.freebasic

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+' version 04-12-2016
+' compile with: fbc -s console
+
+' define true and false for older versions
+#Ifndef TRUE
+#Define FALSE 0
+#Define TRUE Not FALSE
+#EndIf
+
+#Define max 1000000   ' maximum for number to be tested
+
+Function kaprekar(n As ULong) As ULong
+
+    If n = 1 Then Return TRUE
+
+    Dim As ULong x, p1, p2
+    Dim As ULongInt sq = CLngInt(n) * n
+    Dim As String sq_str = Str(sq)
+    Dim As ULong l = Len(sq_str)
+
+    ' decrease the lenght l for every "0"
+    ' at the end of the string
+    For x = l -1 To 1 Step -1
+        If sq_str[x] = Asc("0") Then
+            l = l -1
+        Else
+            Exit For
+        End If
+    Next
+
+    For x = 1 To l -1
+        p2 = Val(Mid(sq_str, x +1))
+        If p2 > n Then
+            Continue For
+        End If
+        p1 = Val(Left(sq_str, x))
+        If p1 > n Then Return FALSE  ' p1 > n leave
+        If (p1 + p2) = n Then Return TRUE
+    Next
+
+End Function
+
+' ------=< MAIN >=------
+
+Dim As ULong n, count
+
+Print "Kaprekar numbers below 10000"
+
+For n = 1 To max -1
+    If kaprekar(n) = TRUE Then
+        count = count + 1
+        If n < 10000 Then
+            Print count, n
+        End If
+    End If
+Next
+
+Print
+Print count;" numbers below "; Str(max);" are Kaprekar numbers"
+
+' empty keyboard buffer
+While Inkey <> "" : Wend
+Print : Print "hit any key to end program"
+Sleep
+End

Task/Kaprekar-numbers/Nim/kaprekar-numbers.nim

@@ -0,0 +1,12 @@
+import strutils, sequtils
+
+proc k(n): bool =
+  let n2 = $(n.in64 * n)
+  for i in 0 .. <n2.len:
+    let a = if i > 0: parseBiggestInt n2[0 .. <i] else: 0
+    let b = parseBiggestInt n2[i .. n2.high]
+    if b > 0 and a + b == n:
+      return true
+
+echo toSeq(1..10_000).filter(k)
+echo len toSeq(1..1_000_000).filter(k)

Task/Kaprekar-numbers/Ring/kaprekar-numbers.ring

@@ -0,0 +1,18 @@
+nr = 0
+for i = 1 to 200
+    if kaprekar(i)
+       nr += 1
+       if i < 201 see "" + nr + " : " + i + nl ok ok
+next
+see "total kaprekar numbers under 200 = " + nr + nl
+
+func kaprekar n
+     s = pow(n,2)
+     x = floor(log(s)) + 1
+     t = pow(10,x)
+     while true
+           t /= 10
+           if t<=n exit ok
+           if s-n = floor(s/t)*(t-1) n = true ok
+     end
+     return (n = 1)

Task/Kaprekar-numbers/Sidef/kaprekar-numbers.sidef

@@ -0,0 +1,19 @@
+require('ntheory')
+var kap = Hash()
+
+15.times { |n|
+    var np = (10**n - 1)
+    %S<ntheory>.fordivisors({ |d|
+        var dp = np//d
+        if (gcd(d, dp) == 1) {
+            kap{ dp == 1 ? d : d.invmod(dp)*d } := 0 ++
+        }
+    }, np)
+}
+
+var nums = kap.keys.map{.to_n}.sort
+
+for n in (6 .. 14) {
+    var np = (10**n - 1)
+    printf("Kaprekar numbers <= 10^%2d:  %5d\n", n, nums.count_by { .<= np })
+}

Task/Kaprekar-numbers/Wortel/kaprekar-numbers.wortel

@@ -0,0 +1,19 @@
+@let {
+  isKap &n [
+    @var s +'' *n n
+    @for i til +1/#s 2 [
+      @vars {
+        fn @+!!s.slice 0 i
+        sn @+!s.slice i
+      }
+      @if =0 sn @break
+      @if =n +fn sn @return [fn sn]
+    ]
+    false
+  ]
+
+  ~[
+    !console.log "Kaprekar numbers below 10000: {!-isKap @to 1TK}"
+    !console.log "Number of Kaprekar numbers below 1000000: {#!-isKap @to 1M}"
+  ]
+}

Task/Kaprekar-numbers/jq/kaprekar-numbers-1.jq

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+# Is the input integer a Kaprekar integer?
+def is_kaprekar:
+    # The helper function acts like a loop:
+    # input is [n, number, str]
+    # where n is the position to be considered next,
+    # number is the integer under consideration,
+    # and str is the string representing number*number
+    def _try:
+      .[0] as $n | .[1] as $number | .[2] as $str
+      | if $n >= ($str|length) then null
+        else   ($str[0:$n] | tonumber) as $left
+             | ($str[$n:]  | tonumber) as $right
+             | if $left > $number then null
+               elif $right == 0 then null
+               elif ($left + $right) == $number then $n
+               else [($n + 1), $number, $str] | _try
+               end
+        end;
+    . as $in
+    | if . == 1 then true
+      elif . < 1 then false
+      else null != ([1, $in, ($in*$in|tostring)] | _try)
+      end ;
+
+# Useful for counting how many times the condition is satisfied:
+def count(generator; condition):
+  reduce generator as $i (0; if ($i|condition ) then .+1 else . end);
+
+def task:
+  [ range(1;10000) | select( is_kaprekar ) ],
+  count( range(1;1000000); is_kaprekar )
+;

Task/Kaprekar-numbers/jq/kaprekar-numbers-2.jq

@@ -0,0 +1,3 @@
+$ jq -n -c -f is_kaprekar.jq
+[1,9,45,55,99,297,703,999,2223,2728,4879,4950,5050,5292,7272,7777,9999]
+54